use strict;

my (@lines1, @lines2, @lines3);
&load_array(\@lines1, "foo1.dat");
&load_array(\@lines2, "foo2.dat");
&load_array(\@lines3, "foo3.dat");

for (my $i = 0; $i < @lines1; $i++) {
        my ($word2) = split(/ /, $lines2[$i]);
        my ($word3) = split(/ /, $lines3[$i]);
        print "$lines1[$i]:$word2:$word3\n";
}

sub load_array($$) {

        my ($a_ref, $file) = @_;
        open (FILE, $file) or die "Can't open $file:$!\n";
        @{$a_ref} = <FILE>;
        close FILE;
        chomp @{$a_ref};
}